The present invention relates to an image read method and apparatus and, more particularly, to an image read method for performing image processes complying with change in shading, and image read apparatus adopting the method.
A film scanner is known as an embodiment of an image processing apparatus for inputting an image recorded on a film to a device, such as a personal computer, which displays the inputted image. A film scanner has been developed for a 135 (35 mm) film. When reading an image, the film scanner first scans an image in a low resolution at high speed, and after the scanned image is displayed by the personal computer (this processing is called "previewing" and the displayed image is called "preview image" hereinafter), an area of the image to be read in a high resolution (main scan area) is designated on the preview image. Then, image data, read in the high resolution, of the image in the designated main scan area is transmitted from the film scanner to the personal computer.
FIG. 30 is a block diagram illustrating a configuration of a conventional film scanner 3000.
In FIG. 30, reference numeral 2801 is a light source; and 2802, a film holder for holding a film as a transparent original image. The film holder 2802 is configured movable in the Y direction. Further, reference numeral 2803 denotes a lens system; and 2804 a CCD linear image sensor (referred to as "CCD" hereinafter), provided in such a manner that the long side of the CCD 2804 is in the Z direction. In this arrangement, the main scanning direction, namely the long-side direction of the CCD 2804, and the sub-scanning direction, which is the moving direction of the film holder 2802, are orthogonal. Here, following combinations between the light source 2801 and the CCD 2804 are available for reading a color image. Namely,
Light Source CCD Type How to read (1) White 3 lines Output R, G and B signals simultaneously (2) Three colors 1 line Output R, G and B signals (R, G, B) in time division (3) White 1 line Output R, G and B signals (R, G, B filters) in time division
The respective combinations have different features and defects, and applications of these combination are often determined by trial and error means. Here, the combination (1) is applied as an example.
Reference numeral 2805 denotes an analog image processing unit where setting of gain and clamping is performed on an analog image signal outputted from the CCD 2804; 2806, an analog-digital (A/D) converter for converting an analog image signal into a digital image signal; 2807, an image processing unit, configured with a gate array, capable of applying various image processes to the digital image signal at high speed and outputting a CCD driving pulse; 2808, a line buffer for temporarily storing image data; 2809, an interface (I/F) ifor communicating with an external device 2810, such as a personal computer; 2811, a system controller, storing program for controlling overall operation in the film scanner 3000, for performing various operation in response to instructions from the external device 2810; 2812, a system bus, configured with an address bus and a data bus, for connecting the system controller 2811, the image processing unit 2807, the line buffer 2808, and the I/F 2809; 2813, a sub-scanning motor, a stepping motor, for moving the film holder 2802 in the sub-scanning direction; 2814, a sub-scanning motor driver for driving the sub-scanning motor 2813 in response to instructions from the system controller 2811; 2815, a sub-scanning position detector for detecting the reference position of the film holder 2802 in the sub-scanning direction by detecting the position of the protuberant shape (not shown) of the film holder 2802 using a photo-interrupter; and 2816, a light-source on/off circuit for turning on and off the light source 2801.
The conventional film scanner 3000 is configured as above, and the film scanner 3000 and the external device 2810, such as a personal computer, communicates by executing software (called "firmware" hereinafter) stored in the system controller 2811 and software (driver software) for controlling the film scanner 3000 by the external device 2810, and image data read by the film scanner 3000 is transmitted to the external device 2810.
FIG. 31 is a flowchart showing an operational sequence of the film scanner 3000 and the external device 2810. Here, it is assumed that both the film scanner 3000 and the external device 2810 are already turned on, the firmware and the driver software are initiated, and the film is already set at a predetermined position.
First in step S2901, previewing is designated by a user through the external device 2810. Upon designating previewing, the external device 2810 transmits various control information, such as type of film, area to be read, and resolution to be used, to the system controller 2811. In the previewing processing, the area to be read is an entire image recorded on the film, and the resolution is set low.
Next, the system controller 2811 prepares for the previewing by setting the information provided in step S2901 from the external device 2810 in step S2902. Thereafter, the process proceeds to step S2903 where the system controller 2811 receives information from the sub-scanning position detector 2815 and controls the sub-scanning motor 2813 so that the film holder 2802 is moved to a predetermined initial position (referred to as "sub-scanning initial position" hereinafter).
Then, in step S2904, the system controller 2811 issues an instruction to turn on the light source 2801 to the light-source on/off circuit 2816, thereby the light source 2801 is turned on. In the succeeding step S2905, the system controller 2811 issues an instruction to output timing signals, such as a CCD driving pulse for reading one line of an image and a RAM address control signal.
Next in step S2906, the image is read line by line by exposing the CCD 2804 for a predetermined period of time while driving the sub-scanning motor 2813 at a predetermined speed. Thereafter, predetermined image processes are performed on the read image data by the image processing unit 2807, and the image data is transmitted to the external device 2810.
After finishing scanning of the designated area of the image in step S2907, the system controller 2811 drives the sub-scanning motor 2813 so as to move the film holder 2802 back to the sub-scanning initial position, and turns off the light source 2801. As soon as all the image data is outputted, the system controller 2811 controls to stop respective functions.
Next, in step S2908, the system controller 2811 is in stand-by state until a next command is received.
In turn, in step S2909, the external device 2810 receives the image data and sequentially displays it on its display screen, thereby providing a preview image to a user.
The process proceeds to step S2910 where the user sets image read (scanning) conditions while watching the preview image on the display screen. Here, similarly to a case where the previewing was designated in step S2901, various information, such as type of the film, area to be read, and resolution to be used, are transmitted to the system controller 2811. Note, in this case, the information for main scanning operation, namely, area to be read designated by the user, and resolution to be used also designated by the user, and so on, are transmitted to the system controller 2811.
In turn, the system controller 2811 receives the image read conditions from the external device 2810 and performs the main scanning under the received image read conditions in step S2911 by repeating the processes in steps S2902 to S2908 as described above.
Thereafter, image data which is transmitted to the external device 2810 is displayed on its display screen as well as stored in a predetermined storage medium (e.g., hard disk, magneto-optical disk, and floppy disk) in step S2912, thereby the entire operation is completed.
However, in the aforesaid conventional film scanner, the user normally does not take a film out of the film scanner until the entire operation is completed; therefore, shading correction data which is taken when performing initialization has to be used until the film is taken out from the film scanner. However, in a case where the film scanner reads images recorded on a single film for long time, the states of the light source changes due to, e.g., change in environmental temperature and change in voltage of electric power supplied to the light source. As a result, in the conventional image scanner, an optimized shading correction is not always performed, which causes deterioration of image quality.